Who among us can truly claim to know the secrets of the human heart? Not many. And perhaps even fewer since the weekend and the broadcasting of Living With ... Karl and Yvette (Living).

Yvette is Yvette Fielding, youngest ever Blue Peter presenter (1987-92) and, for those of us whose memories stretch yet further back, Sandy in the children's BBC series Seaview, who had a string of delightful non-adventures growing up in her parents' Blackpool guesthouse. Karl is the cameraman she met while working on City Hospital and who proposed to her live on screen 10 years ago. They have co-produced two children and several series of Most Haunted. As the old saying goes, the family that visits spooky locations round Britain trying to document paranormal activity stays together.

Yvette loves Karl. Except when he makes broomstick jokes about her mum. "I love me mum. Some broomstick jokes are fine, but he goes too far!" Karl acknowledges that he has a problem with jokes. "Toilet humour is actually too highbrow for me. Quite often, people laugh out of sympathy, but that's not quite the same, is it?" There are many scenes in which people around Karl are not laughing at all.

Still, it is the duty of a good wife to persist, gently, stealthily, in curbing her husband's excesses and rendering him acceptable to society. And Yvette does try. "What are you like, Karl!" she will screech fondly as they perambulate the grounds of their 17th-century farmhouse. "Will you get off me bum!?"

They are both bereft when he has to go away for a fortnight to scout locations in the US. When he comes back early, Yvette sobs with delight. I checked her face. It really was sobbing. It really was delight. When she turns 40, he arranges a surprise medieval-banquet birthday party for her and, as she enthuses to camera, he appears at her side with a champagne stopper. "She keeps popping my cork!" he interrupts, pitching it up into the air. She laughs delightedly. It is possible we will never understand.